The present invention generally relates to wireless communication networks, and particularly relates to user scheduling in such networks.
In some types of wireless communication networks, access terminals share the air interface between the terminals and the network. High data rate (HDR) networks configured according to the TIA/EIA/IS-856 standard exemplify this shared interface concept. With shared forward link resources, the network serves only one access terminal in a group at any given instant. By rapidly switching service between the terminals, the plurality of terminals is simultaneously, albeit discontinuously, served by the network. Deciding which terminal to serve in any given service interval is the function of a “scheduler.” The scheduler typically comprises program logic or software services intended to fulfill this function. Scheduling operations are typically governed by a service goal or constraint.
Selecting the “best” user for service at each scheduling decision point is an optimization problem. In optimization problems, utility functions are used to characterize the cost or benefit of a change. In scheduling air interface usage, utility functions define the utility of serving individual users. The optimization problem becomes one of maximizing an objective function whose value is dependent upon the set of utility functions. A scheduler repeatedly evaluates the objective function to move towards an optimum schedule for sharing the limited resources of the air interface between active users.
Past approaches to network scheduling the use of shared resources within a communication network include so-called “proportional fair” scheduling techniques. Proportional fair scheduling seeks to maximize the objective function, and is essentially a maximum dual-ascent approach that reduces to finding the direction of maximum gradient for the objective function at each scheduling decision point.
While proportional fair scheduling works well in some circumstances, its use places overly limiting restrictions on the nature of utility and objective functions that may be defined for serving users. These restrictions hamper a service provider's flexibility in terms of denying scheduling flexibility. Thus, alternative approaches that offer additional flexibility or impose fewer constraints on the type or types of scheduling functions that may be used are needed.